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DTC 14: Stoplight Switch System: Diagnosis

WARNING: This page is about a different car, the 2004 Mitsubishi Eclipse. However, it is still accessible from the selected car via links, so may be relevant.

Required Special Tool:

  1. Check the output circuit voltage at stoplight switch connector C-03 (terminal number 3) by backprobing.
    1. Do not disconnect stoplight switch connector C-03.
    2. Turn the ignition switch to the "ON" position.
    3. Measure the voltage between terminal 3 and ground by backprobing.
      Fig 1: Measuring Voltage Between Terminal 3 And Ground By Backprobing
      G03303059Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    4. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Is the voltage approximately battery positive voltage?

    YES : Go to Step 3.

    NO : Go to Step 2.

  2. Check stoplight switch connector C-03.
    Fig 2: Locating Connector C-03
    G03303060Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the connector damaged?

    YES : Repair or replace connector. Refer to HARNESS CONNECTOR INSPECTION . Then check that diagnostic trouble code 14 is not output.

    NO: Go to Step 13.

  3. Check the output circuit voltage at stoplight switch connector C-03 (terminal number 4) by backprobing.
    1. Do not disconnect stoplight switch connector C-03.
    2. Turn the ignition switch to the "ON" position and the auto-cruise control main switch to the "ON" position.
    3. Measure the voltage between terminal 4 and ground by backprobing.
      Fig 3: Measuring Voltage Between Terminal 4 And Ground By Backprobing
      G03303061Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    4. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Is the voltage approximately battery positive voltage?

    YES : Go to Step 6.

    NO : Go to Step 4.

  4. Check stoplight switch connector C-03.
    Fig 4: Checking Stoplight Switch Connector C-03
    G03303062Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the connector damaged?

    YES : Repair or replace connector. Refer to HARNESS CONNECTOR INSPECTION . Then check that diagnostic trouble code 14 is not output.

    NO : Go to Step 5.

  5. Check the stoplight switch.
    1. Disconnect stoplight switch connector C-03.
    2. Connect an ohmmeter to the stoplight switch between terminals 3 and 4, and check whether there is continuity when the plunger of the stoplight switch is pushed in and an open circuit when it is released.
      Fig 5: Checking Stoplight Switch
      G03303063Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    3. The stoplight switch is in good condition if the circuit is open when the plunger is pushed in to a depth of within 4 mm (0.2 inch) from the outer case edge surface, and if there is continuity when it is released.
      Fig 6: Checking Stoplight Switch Continuity
      G03303064Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the circuit is open?

    YES : Replace the stoplight switch. Refer to DISC & DRUM article. Then check that a diagnostic trouble code 14 is not output.

    NO : Check that diagnostic trouble code 14 is not output. If diagnostic trouble code 14 is output, replace the auto-cruise control-ECU (Refer to AUTO-CRUISE CONTROL .). Then check that diagnostic trouble code 14 is not output.

  6. Check the output circuit voltage at auto-cruise control vacuum pump connector A-01 (terminal number 1) by backprobing.
    1. Do not disconnect auto-cruise control vacuum pump connector A-01.
    2. Turn the ignition switch to the "ON" position and the auto-cruise control main switch to the "ON" position.
    3. Measure the voltage between terminal 1 and ground by backprobing.
      Fig 7: Measuring Voltage Between Terminal 1 And Ground By Backprobing
      G03303065Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    4. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Is the voltage approximately battery positive voltage?

    YES : Go to Step 8.

    NO : Go to Step 7.

  7. Check auto-cruise control vacuum pump connector A-01 and intermediate connector C-06.
    Fig 8: Locating Connector A-01
    G03303066Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    Fig 9: Locating Connector C-06
    G03303067Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is any connector damaged?

    YES : Repair or replace connector. Refer to HARNESS CONNECTOR INSPECTION . Then check that diagnostic trouble code 14 is not output.

    NO : Check the harness wire between stoplight switch connector C-03 and auto-cruise control vacuum pump connector A-01 for open circuit or damage. Then repair if necessary. Then check that diagnostic trouble code 14 is not output.

  8. Check the output circuit voltage at auto-cruise control-ECU connector C-20 (terminal numbers 7, 8 and 16) by backprobing.
    1. Do not disconnect auto-cruise control-ECU connector C-20.
    2. Turn the ignition switch to the "ON" position and the auto-cruise control main switch to the "ON" position.
    3. Measure the voltage between terminal 7 and ground by backprobing.
      Fig 10: Measuring Voltage Between Terminal 7, 8 ,16 And Ground By Backprobing
      G03303068Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      • Voltage should be battery positive voltage. [When decelerating with the "SET" switch while driving at constant speed (Release valve open).]
    4. Measure the voltage between terminal 8 and ground by backprobing.
      • Voltage should be battery positive voltage. [When decelerating with the "SET" switch while driving at constant speed. (Control valve open).]
    5. Measure the voltage between terminal 16 and ground by backprobing.
      • Voltage should be battery positive voltage. (When the motor is stopped during a constant road speed.)
    6. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Are all of the above values satisfied?

    YES : Check that diagnostic trouble code 14 is not output. If diagnostic trouble code 14 is output, replace the auto-cruise control-ECU (Refer to AUTO-CRUISE CONTROL .). Then check that diagnostic trouble code 14 is not.

    NO : Go to Step 9.

  9. Check auto-cruise control-ECU connector C-20 and intermediate connector C-94.
    Fig 11: Locating Connector C-20
    G03303069Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    Fig 12: Locating Connector C-94
    G03303070Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the connector damaged?

    YES : Repair or replace connector. Refer to HARNESS CONNECTOR INSPECTION . Then check that diagnostic trouble code 14 is not output.

    NO: Go to Step 10.

  10. Check auto-cruise control vacuum pump connector A-01.
    Fig 13: Checking Auto-Cruise Control Vacuum Pump Connector A-01
    G03303071Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the connector damaged?

    YES : Repair or replace connector. Refer to HARNESS CONNECTOR INSPECTION . Then check that diagnostic trouble code 14 is not output.

    NO: Go to Step 11.

  11. Check the auto-cruise vacuum pump.
    1. Disconnect the vacuum hose from the auto-cruise vacuum pump and connect a vacuum gauge to the vacuum pump.
      2. Fig 14: Checking Auto-Cruise Vacuum Pump
      G03303072Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    2. Disconnect the vacuum pump connector.
    3. Check the auto-cruise vacuum pump and valves according to the following procedure:
      • Connect the positive battery terminal to auto-cruise vacuum pump connector terminal 1, and the negative battery terminal to terminals 2, 3, and 4. The vacuum gauge should read 27 kPa (8.0 in Hg) or more.
      • The vacuum should be maintained when terminal 4 is disconnected from the negative battery terminal while terminals 1, 2, and 3 remain connected. Then the vacuum gauge should read 0 kPa (0 in Hg) when terminal 2 is disconnected from the negative battery terminal while terminals 1, and 3 remain connected.
      • The vacuum should be maintained when terminal 4 is disconnected from the negative battery terminal while terminals 1, 2, and 3 remain connected. Then the vacuum gauge should read 0 kPa (0 in Hg) when terminal 3 is disconnected from the negative battery terminal while terminals 1, and 2 remain connected.

    Q: Are all of the above values satisfied?

    YES : Go to Step 12.

    NO : Replace the auto-cruise vacuum pump (Refer to AUTO-CRUISE CONTROL .). Then check that diagnostic trouble code 14 is not output.

  12. Check the harness wire between auto-cruise control vacuum pump connector A-01 (terminal numbers 2, 3 and 4) and auto-cruise control-ECU connector C-20 (terminal numbers 7, 8 and 16).
    Fig 15: Locating Connector A-01
    G03303073Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    Fig 16: Locating Connector C-20
    G03303074Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is any harness wire between auto-cruise control vacuum pump connector A-01 (terminal numbers 2, 3 and 4) and auto-cruise control-ECU connector C-20 (terminal numbers 7, 8 and 16) damaged?

    YES : Repair harness wire and then check that diagnostic trouble code 14 is not output.

    NO : Check that diagnostic trouble code 14 is not output. If diagnostic trouble code 14 is output, replace the auto-cruise control-ECU (Refer to AUTO-CRUISE CONTROL .). Then check that diagnostic trouble code 14 is not output.

  13. Check the output circuit voltage at auto-cruise control-ECU connector C-20 (terminal number 5) by backprobing.
    1. Do not disconnect auto-cruise control-ECU connector C-20.
    2. Turn the ignition switch to the "ON" position and the auto-cruise control main switch to the "ON" position.
    3. Measure the voltage between terminal 5 and ground by backprobing.
      Fig 17: Measuring Voltage Between Terminal 5 And Ground By Backprobing
      G03303075Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    4. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Is the voltage approximately battery positive voltage?

    YES: Go to Step 14.

    NO: Go to Step 15.

  14. Check intermediate connector C-89.
    Fig 18: Checking Intermediate Connector C-89
    G03303076Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the connector damaged?

    YES : Repair or replace connector. Refer to HARNESS CONNECTOR INSPECTION . Then check that diagnostic trouble code 14 is not output.

    NO : Check the harness wire between auto-cruise control-ECU connector C-20 and stoplight switch connector C-03 for open circuit or damage. Then repair if necessary. Then check that diagnostic trouble code 14 is not output.

  15. Check auto-cruise control-ECU connector C-20.
    Fig 19: Locating Connector C-20
    G03303077Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the connector damaged?

    YES : Repair or replace connector. Refer to HARNESS CONNECTOR INSPECTION . Then check that diagnostic trouble code 14 is not output.

    NO : Check that diagnostic trouble code 14 is not output. If diagnostic trouble code 14 is output, replace the auto-cruise control-ECU (Refer to AUTO-CRUISE CONTROL .). Then check that diagnostic trouble code 14 is not output.

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